The present invention relates to a method for imparting improved surface properties to a polymeric shaped article or, more particularly, to a method for imparting improved susceptibility to adhesive bonding to a shaped body of a synthetic polymer having aromatic rings and nitrogen atoms in the backbone chain of the polymer molecule.
There are known several industrially important synthetic polymers having aromatic rings and nitrogen atoms in the backbone chain of the polymer molecule including various kinds of polyimides, polyamidoimides, polyaramides, i.e. aromatic polyamides, and the like (hereinafter referred to as nitrogen-containing aromatic polymers). Shaped articles of these synthetic polymers are excellent in various properties such as mechanical strengths, electric properties, heat and cold resistance, wearing resistance, lightness, moldability, resistance against chemicals, intoxicity and the like so that they are useful as electric insulating materials, parts for electric and mechanical instruments, sound insulating materials, laminated plates, sandwich panels, boards, carpets, woven cloths, protection wears, heat-insulating wears, belts, tire cords for automobiles, ropes and the like materials in a variety of fields.
There are many applications, meanwhiile, in which the shaped articles of these polymers are used as a component of a composite material as integrally combined with the other types of polymeric materials in addition to the applications in which the shaped articles of these polymers are separately used as such in the forms of films, plates, tubes and the like. When such a combined use as a component of a composite material is intended, firmness in adhesive bonding is essential between the nitrogen-containing aromatic polymer and the other polymer combined therewith whereas the conventional nitrogen-containing aromatic polymers are defective in this respect so that composite materials formed thereof are sometimes inferior in the mechanical and electric properties with the advantages expected to the composite structure exhibited not to a full extent. For example, the polymers or, in particular, polyaramide resins are excellent as a polymeric material in the mechanical and electric properties and useful as a reinforcing material for another synthetic resin as a matrix in the forms of single filaments, chopped yarns, woven cloths and the like while a problem sometimes noted in such an application is the poor adhesive bonding between the matrix resin and the reinforcing material so that improvement in this regard has been eagerly desired.
Of course, there have been made various attempts and proposals for the improvement of the adhesive bonding in these reinforcing materials including a method of treating the material in advance with an acid or alkali, a method of providing an undercoating to the reinforcing material with another resin susceptible to firm adhesive bonding and a method of subjecting the surface of the reinforcing material to be treatment with corona discharge although none of these methods is quite effective for the purpose.